Hey! I've worked in restaurants for a few years now and what people generally don't know about servers is that we have to tip out the kitchen on our sales. This means that regardless of what people tip on their bill, we have to tip the "house" a certain percent of the bill (at least in Canada and I'm pretty sure this is standard in the U.S. too). Typically tip out is 5%, so on a take-out order, ​you should at least tip 5% so the server doesn't have to pay out of their pocket for you to get take-out!